Mix design The precise recipe of cement, water, sand, gravel, and chemical additives used to create concrete with specific strength and durability properties.
Standard concrete mixes won't pass muster in New York City. The NYC DOT requires a specific concrete mix design that is highly resistant to winter salt and heavy freeze-thaw cycles. This mix is designed to achieve over 4,000 PSI of compressive strength within 28 days of pouring, ensuring the sidewalk lasts for decades.
Frequently Asked Questions About Mix design
What is a concrete mix design?
The specified proportions of cement, water, sand, aggregate and admixtures that produce concrete with the required strength and durability.
Why does NYC need a specific mix?
City sidewalks face repeated freeze-thaw cycles and heavy de-icing salt exposure, so the mix must be air-entrained and durable, not just strong.
What strength is targeted?
A specified compressive strength measured at 28 days, set by the applicable DOT specification for the type of work.
Can a contractor substitute a cheaper mix?
Not without violating the specification. The delivery ticket documents what was actually supplied, which is why it is worth keeping.